'Desert dust' days may worsen kids' asthma

NEW YORK (Reuters Health) - Dust blown from faraway deserts may accumulate in the air to levels great enough to contribute to children's asthma attacks, a new study suggests.

It's well established that poor air quality can worsen symptoms in people with asthma or other lung disease, and children are thought to be particularly susceptible due to factors like their smaller airways and less developed immune systems.

One recent study in the Atlanta area found that on days where levels of ozone and certain traffic pollutants were highest, the rate of children's ER visits for asthma attacks also rose.

Little has been known, however, about the potential effects of a nature-made air contaminant -- desert dust.

The dust, which contains quartz and other substances and microorganisms that may cause airway inflammation, is transported globally; dust from the Sahara in Africa, for example, can be carried across the Atlantic to the Americas.

For the new study, researchers looked at the relationship between "heavy dust events" and hospital admissions for asthma among children in Toyama, Japan -- a region with a population of about 1 million people that in the spring is susceptible to receiving dust from storms in the deserts of China and Mongolia.

They found that between 2005 and 2009, the region had a total of six heavy-dust days from February through April -- when mineral-dust levels in the air were above 1 milligram per cubic meter.

During that same time frame, 620 children between the ages of 1 and 15 were hospitalized for an asthma exacerbation. In general, children's risk of being hospitalized was 88 percent higher on a heavy-dust day compared with other days, and similarly elevated during the week following a major dust event.

The findings, reported in the American Journal of Respiratory and Critical Care Medicine, do not prove that the desert dust itself caused excess asthma attacks.

But the researchers did account for levels of pollen and air pollutants like nitrogen dioxide and small particles other than mineral dust, and the link between desert dust and asthma hospitalizations remained.

Because there were only a handful of heavy-dust days during the study period, only a small number of asthma hospitalizations would be attributable to the air-quality condition, noted lead researcher Dr. Kumiko T. Kanatani, of the Kyoto University Graduate School of Medicine in Japan.

However, in parts of the world more affected by desert dust, such days may be a more important contributor to children's asthma exacerbations, Kanatani told Reuters Health by email.

For parents of children with asthma, the findings underscore the importance of keeping an eye on local air quality, according to Kanatani.

While there may be no advisories on desert dust specifically, levels of so-called particulate matter -- especially "coarse" dust particles known as PM10 -- also rise on heavy-dust days, Kanatani noted.

And levels of particulate matter are monitored and included in local air-quality indices -- which, in the U.S., are those color-coded systems used to alert the public as to whether the day's air quality is "good," "moderate," unhealthy for people with lung disease or other chronic conditions, or potentially unhealthy for all.

According to Kanatani, a hazy sky is a good initial clue that levels of particulate matter are high that day, and it may be a good idea to limit asthmatic children's time outdoors. But parents can also go online to check local PM levels, the researcher noted.

In the U.S., local news outlets generally provide daily air-quality indices; they are also available on the government Web site AIRNow, at http://www.airnow.gov.